1. Field of the Invention
The present invention generally relates to an inductor structure, in particular, to an inductor structure with an improved induction quality.
2. Description of Related Art
Generally speaking, inductors can store/release energy under the condition of electromagnetic conversion, and the inductors may be used as elements for stabilizing current. In addition, in integrated circuits (IC), the inductors play an important role but are challenging elements. The inductors have wide applications, for example, in radio frequency (RF). In the high-frequency application, the inductor is required to have a very high quality, i.e., the inductor must have a high quality factor denoted by a Q value. The Q value is defined as follows:Q=ω×L/R where ω is the angular frequency, L is the inductance of a coil, and R is the resistance at a specific frequency taking the inductance loss into account.
Generally speaking, a variety of methods and techniques have been proposed for integrating inductors with IC processes. However, in the ICs, the limitation of the thickness of the inductor conductor and the interference of the silicon substrate to the inductor will also lead to unsatisfactory inductor quality. In the prior art, a thick metal is disposed on the top layer of the inductor to reduce the conductor loss, so as to improve the Q value of the inductor.
However, the inductor structure with a thick metal disposed on the top layer thereof is still affected by an eddy current. Since the region with the largest magnetic flux is located in the inner turn of the inductor structure, and especially the impact of the eddy current on the bends of the inner turn is most severe, the uniformity of the current in the inner turn is poor, and the cross-sectional area of the conductor cannot be fully used. Therefore, the inductor quality is degraded.